Kompany didn't play in his team's final group stage game against South Korea. He returned to training yesterday, according to Belgian newspaper HLN, but his status is still uncertain.

It'd be significant if he didn't play.

Kompany is the most important player on a Belgium defense that has yet to give up a goal from the run of play during the World Cup. While centerback is an area of depth for Belgium — Thomas Vermaelen, Nicolas Lombaerts, and Daniel Van Buyten are all serviceable players — they don't have a player with Kompany's combination of pace, power, and experience.

Even without Kompany's injury, the Belgians are banged up in defense. Anthony Vanden Borre broke his leg and is out for the World Cup. Vermaelen is also carrying a leg injury and is uncertain for the U.S. game. If all three players are out, Belgium would go into the Round of 16 with five healthy defenders on the roster and little flexibility.